We run over 200 Dell Poweredge Server to support our business. We are about to conduct a mandatory electrical test that requires us to power down servers to critical systems. To avoid this we are planning on using a pair of synronised 125KVa generators. What I want to know is can I leave the normal feed from the main supply plugged into and running the server, bring up the generator supply and plug it into the alternative supply to the server and then remove the normal feed, without powering down the server. Whilst understanding that the supplies will not be in phase?
If all of your PowerEdge Servers have redundant PSUs, you can leave the main supply going to a PDU then to one of the server's PSU. Next, you can take the generator's supply into a different PDU then to the other PSU on the server. After doing this for each server in your farm, you should have power coming from two independent sources to your servers. And in doing so, you should be able to remove the normal feed without powering down the servers.
Finally, given the # of servers in your environment, I would recommend verifying the process on a single 42U rack before repeating the process for the rest of your datacenter.